﻿using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Encoder = System.Drawing.Imaging.Encoder;

namespace laohan.Common.Common
{
    /// <summary>
    /// 
    /// </summary>
    public class ImageCompression
    {
        /// <summary>
        /// GetEncoderInfo
        /// </summary>
        /// <param name="mimeType"></param>
        /// <returns></returns>
        private static ImageCodecInfo GetEncoderInfo(string mimeType)
        {
            ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();

            for (int i = 0; i < encoders.Length; ++i)
            {
                if (encoders[i].MimeType == mimeType)
                {
                    return encoders[i];
                }
            }

            return null;
        }

        /// <summary>
        /// 图片压缩(降低质量以减小文件的大小)
        /// </summary>
        /// <param name="srcBitmap">传入的Bitmap对象</param>
        /// <param name="destStream">压缩后的Stream对象</param>
        /// <param name="level">压缩等级，0-100</param>
        private static void Compress(Bitmap srcBitmap, Stream destStream, long level)
        {
            ImageCodecInfo myImageCodecInfo;
            Encoder myEncoder;
            EncoderParameter myEncoderParameter;
            EncoderParameters myEncoderParameters;

            // Get an ImageCodecInfo object that represents the JPEG codec.
            myImageCodecInfo = GetEncoderInfo("image/jpeg");

            // Create an Encoder object based on the GUID

            // for the Quality parameter category.
            myEncoder = Encoder.Quality;

            // Create an EncoderParameters object.
            // An EncoderParameters object has an array of EncoderParameter
            // objects. In this case, there is only one

            // EncoderParameter object in the array.
            myEncoderParameters = new EncoderParameters(1);

            // Save the bitmap as a JPEG file with 给定的 quality level
            myEncoderParameter = new EncoderParameter(myEncoder, level);
            myEncoderParameters.Param[0] = myEncoderParameter;
            srcBitmap.Save(destStream, myImageCodecInfo, myEncoderParameters);
        }

        /// <summary>
        /// 图片压缩(降低质量以减小文件的大小)
        /// </summary>
        /// <param name="srcFile"></param>
        /// <param name="destFile"></param>
        /// <param name="level"></param>
        public static void Compress(string srcFile, string destFile, long level)
        {
            using (Image image = Image.FromFile(srcFile))
            {
                using (Bitmap bitmap = new Bitmap(image))
                {
                    using (FileStream destStream = new FileStream(destFile, FileMode.Create))
                    {
                        Compress(bitmap, destStream, level);
                    }
                }
            }
        }
    }
}
